Many people who use computers in their day-to-day business are not computer experts. It would often be counter-productive to require them to be; they are needed for their other skills. As a result one of the challenges in designing software applications that will be used on computer workstations is to ensure that the users of such software can perform the tasks of their jobs rapidly and efficiently. If the user interface for an application is complex or confusing then an organization may provide significant training for their employees to use the application and may supply help desk personnel to deal with queries and problems; both of which may reduce productivity and increase the total cost of using the software.
Over the past few decades it has become commonplace to represent page-based documents on a computer display in a roughly consistent way, often as a more-or-less white rectangle with the same aspect ratio as a printed page, shown against a gray, black or colored background. As a result of consistent usage computer users are now familiar with this representation of a simple stream of pages. In the same way the use of scroll bars and “page up” and “page down” keys has become a part of the baseline knowledge that new staff may be expected to already understand. These commonly understood representations and methods of interaction do not, however, extend to a more complex collection of documents that is more than a simple, ordered, sequence of pages.